Russia's prime minister Dmitry Medvedev might have eased the nerves of the country's dairy cows by scrapping daylight saving but it is stressing out the nation's traders.

Trading on the Russian stock exchange has dropped 15% since London put the clocks back an hour last month and Moscow did not follow suit.

Medvedev took the decision to scrap daylight saving last year after farmers complained that it upsets the rhythm of dairy cows. But traders complain that the increase in the time difference between London and Moscow from three to four hours is hampering plans to expand Russia's role in global finance.

Trading on Russia's Micex exchange fell to an average 37bn shares a day in the 11 days following London's switch to GMT on October, compared to 43bn in the previous 11 days, according to data from Bloomberg. Foreigners own about two-thirds of all Russian shares available for trading, according to Citigroup.

"The time difference is responsible for the low volumes," Andrey Vashevnik, chief investment officer at R&B Investment Fund told Bloomberg in Moscow. "It prevents people from doing business in the morning."

Dmitry Ryzhkov, vice-president of equity sales at Moscow's Alfa Bank, said: "Traders are stressed out. I would very enthusiastically support the return to time changes."

Tatyana Rybalova, head of the research centre of Russia's National Union of Milk Producers, explained that cows are much more sensitive to the changing of the clocks than humans. "I remember when daylight saving time was introduced in the Soviet times, there were protests by milkmaids in Novosibirsk and Omsk. It seemed to particularly upset the cows in Siberia," he told the Guardian last year.

The time change is also said to adversely affect Russian people. "During the period of the clocks changing, the number of heart attacks increases by 50% and the number of suicides by 66%," said Arkady Tishkov, a geography professor and member of the working group that advised cancelling twice-yearly time adjustments.